Thermopower and resistivity of the topological insulator Bi 2 Te 3 in the amorphous and crystalline phase

We have, in-situ, prepared and measured the temperature dependence of thermopower ( ) and resistance ( ) of Bi Te topological insulator (TI) thin films in the amorphous and crystalline phase. Samples were prepared by sequential flash-evaporation at liquid He temperature. The ( ) in the amorphous phase is negative and much larger compared to other known amorphous materials, while in the crystalline phase it is also negative and behaves linearly with the temperature. The resistivity ( ) in the amorphous phase shows a semiconducting like behavior that changes to a linear metallic behavior after crystallization. ( ) an ( ) results in the crystalline phase are in good agreement with results obtained both in bulk and thin films reported in the literature. Linear behavior of the ( ) for > 15K indicates the typical metallic contribution from the surface states as observed in other TI novel materials. The low temperature conductivity < 10K exhibits logarithmic temperature dependent positive slope ∼ 0.21, indicating the dominance of electron-electron interaction (EEI) over the quantum interference effect (QIE), with a clear two dimensional nature of the contribution. Raman spectroscopy showed that the sample has crystallized in the trigonal 3 space group. Energy-dispersive X-ray spectroscopy reveales high homogeneity in the concentration and no magnetic impurities introduced during preparation or growth.